Ground based in situ observations of ammonium at Pallas (Matorova) (FI0036R) using filter_3pack. These measurements are gathered as a part of the following projects AMAP, EMEP and they are stored in the EBAS database (http://ebas.nilu.no/). Parameters measured are: ammonium in aerosol (mass_concentration_of_ammonium_expressed_as_nitrogen_in_dry_aerosol_particles_in _air), ammonium in aerosol (mass_concentration_of_ammonium_in_dry_aerosol_particles_in _air)